An injection machine typically includes an injection head or mechanism for injecting moldable material into a mold. In the case of a sand core molding machine that produces sand cores for use in producing cast parts, molding sand containing a hardening agent is injected by an injection head into a core box. The injection head includes a feed tube, an injection bell mounted on the bottom of the feed tube and an injection plate secured to the injection bell. The injection plate includes orifices aligned with bores in the core box through which the molding sand is blown. When a different core box is to be used to produce cores, the injection plate typically must be replaced by a different injection plate inasmuch as different core boxes have different bore configurations for the admittance of sand therein. The need to frequently change the injection plate has resulted in the development of clamping apparatus for removably securing the injection plate to the injection bell. Such clamping apparatus has taken the form of brackets or hooks carried by the injection bell that are manually movable to a clamping position to clamp the injection plate to the bell.
In conventional molding machines of the above type, a single size bell is used regardless of the dimensions of the core box in which the cores are to be formed. Thus, for example, the same injection bell is used to produce cores in a relatively narrow vertically parting core box or a relatively wide horizontally parting core box. Since the same bell is used to inject sand in core boxes of varying widths, the bell must be sized to accommodate the core box having the widest dimension. When the bell is used to inject sand in core box having a lesser width, molding sand tends to accumulate and harden in the outer margins of the injection bell. This accumulation is undesirable since it results in the need for frequent cleaning of the bell, thereby increasing the down time of the machine. Also, adjustments must be made to the injection head when a different plate is to be used. This changeover time also reduces the productivity of the machine.